class Animal(object):
    def run(self):
        print("Animal is running")

class Dog(Animal):
    def run(self):
        print("Dog is running")

class Cat(Animal):
    def run(self):
        print("Cat is running")

dog = Dog()
dog.run()

cat = Cat()
cat.run()

def run_twice(animal):
    animal.run()
    animal.run()

run_twice(Animal())
run_twice(Dog())